Fumonisins : chromatographic methodology and their role in human and animal health

Bibliography: pages 221-243.The fumonisins consist of a group of 7 structurally related mycotoxins originally isolated from Fusarium moniliforme, a fungal contaminant of maize worldwide. The incidence of F. moniliforme in home-grown maize, has been associated with human oesophageal cancer (OC) risk in the Transkei and China. Fumonisin B₁ (FB₁), the major fumonisin analogue, exhibits both cancer-initiating and -promoting activities, and has been shown to induce a number of disease syndromes in different animal species. Two other fumonisin analogues, fumonisins B₂ (FB₂) and B₃ (FB₃) also exhibit cancer-initiating potentials, similar to those observed for FB₁. A method, developed at PROMEC, for the analytical determination of FB₁ and FB₂ in maize, based on ion-exchange purification of crude extracts, derivatisation, reversed-phase liquid chromatography separation and fluorescence detection, was subjected to an international collaborative study involving 11 laboratories from 6 countries. Although the results established that the method was highly reproducible, alterations were made in order to reduce analysis time, identify and eliminate potential sources of error and include the co-determination of FB₃. Both methods were used, in conjunction with confirmatory techniques, to determine the extent of animal and human exposure to the fumonisins. Naturally occurring fumonisin levels in animal feeds, were used in conjunction with hazard assessment data, to establish fumonisin tolerance guidelines for selected animal species. The results indicated that combined fumonisin concentrations in feeds of 10 and 100 μg/g (ppm) should be regarded as potentially harmful to horses and swine, respectively. Human exposure assessment was based on data from various sources, including the 1989 and 1990 South African maize crops, maize imported into South Africa, retail maize-based foods from 14 countries, and home-grown maize from the Transkei. The data indicated that fumonisin contamination occurs worldwide, while the levels to which populations are exposed differ considerably. A statistical association was established between fumonisin contamination of home-grown maize, and the prevalence of human OC in the Transkei, where humans can be exposed to fumonisin levels that would be deemed harmful to both horses and swine

Pådriverne bak diversitet og utbredelse av villbier i en artsfattig region

Bee diversity is declining globally. On a European scale, roughly 10% of the species are considered threatened, but the number may be even higher. The threatened status of bees depends on both the taxonomic and spatial scale. For instance, a relatively high proportion of species within the cold adapted Bombus are expected to decline due to global warning. Moreover, numbers may differ among regions and about 25% of the bee species in Norway are considered threatened. Halting or reversing this decline requires that we understand the main drivers of bee diversity within regions. Species-poor regions where the autecology of species are relatively well known may provide valuable model systems for studying the processes behind community assembly. Indeed, due to the low numbers of species and steep environmental gradients one may expect a relatively rapid species turnover over short geographic distances in Norway. The aim of this thesis was to identify important drivers of bee diversity in Norway. Bee-flower networks from different regions of the world were used to test for the influence of global scaled processes on community assembly (Paper I). We tested if the phylogenetic turnover among Bee-flower networks (i.e. bee communities) increased with geographic distances, thus indicating an influence of speciation and migration, and with dissimilarities in climatic conditions, thus indicating global ecological filtering. We also tested if the niche overlap, in terms of visitations to plant species, was determined by the bee phylogeny, thus indicating within community ecological filtering. We used bee communities sampled in power line clearings surrounded by boreal forests as model systems for studying the influence of dispersal limitation, ecological filtering and ecological drift on the distribution of species within the metacommunity (Papers II-V). We established an experiment within this system to test how, and under which conditions, different management practices could improve power line clearings for wild bees (Paper IV)

Living on the edge the value of field edges as resource patches for solitary bees (Hymenoptera: Apiformes)

Current patterns of anthropogenic land-use are reducing the diversity of pollinators through habitat destruction, degradation and landscape simplification. This may adversely affect both wild and domesticated flowering plants through pollen limitation. These concerns are supported in the parallel declines in solitary bees and wild plants observed in Europe. Solitary bees vary in their requirements to nesting, mating and forage sites. In addition, bee assemblages fluctuate over years. Successful management of remnant habitat patches therefore requires both the consideration of autecological traits and temporal patterns in bee diversity. In this study I sampled bees to evaluate the potential value of field edges in the Norwegian agricultural matrix. I found that bee species were not randomly distributed in the landscape. Furthermore, the solitary bee assemblages were relatively stable between years but could be grouped by monthly affiliations. I isolated two groups of bee assemblages, one consisting of spring active bees and one of summer active bees. Furthermore I found group-specific responses to habitat conditions. The species richness and abundance of the spring-active group was negatively related to the proportion of agricultural land around the field edge, whereas the summer-active group preferred sunexposed field edges with short vegetation and a high floral richness. The group-specific responses reflect seasonal changes in the predominant bee species phenology. The spring group was mainly composed of Andrena species which burrow nests in the ground and find forage in spring blossoming trees such as Salix caprea Linnaeus. which are common in non-agricultural landscape types. In contrast, the summer group was more diverse in phenology and occurred at a time when the floral resources were more diverse. These results suggest that field edges can provide an important asset in the conservation of solitary bees. The success of such management does however call for more research on the temporal variation in the autecology of bees